40 SW AOL - Plunk Test vs Wilson Cart Gage

[Pugsbrew]

OK, not trying to start a .001 reloading war. I just want to know a few things. I have reloaded for revolvers, years ago. Reloading then made since in regards to cartridge length. Now that I’m trying to reload semi-auto’s, there seems to be a plethora of data/facts/whams/etc on cart length (CL). The reason I will use CL is because there are so many terms in regards to the overall length of the cartridge, so bare with me. Please no negative comments on this.

So, I am going to start reloading the 40 SW. I have a Wilson Cartridge Gage tool and an OEM and Lone Wolf replacement barrel for my Glock. Please, no comments on the Glock. I’m using these devices to see if the cartridge will work.

The “Plunk Test” and the Gage do not agree on what it is telling me. I made a mock up round with the following components and dimensions (for those that want to know the numbers):

Precision Delta 180 gr FMJFP bullets
Length .590
Dia .400

Case Winchester length .844, outside case dia with bullet seated .421

The overall cartridge length is 1.135

OK, the round will “plunk” fine in the barrels, but will not drop in to the Wilson Gage. In the Wilson Gage (WG), the entire rim is proud of the gage. Now, factory ammo drop all the way in to the WG, the end of the cartridge is flush with the end of the gage. I did apply a Lee FCD crimp to the mock cartridge just to see if that made a difference, it did not.

OK, enough of this. The mock cartridge drops fine in my barrels, compared to all commercial cartridges, and the “Plunk Test” pictures. So, now for the questions.

Again, I am new at reloading semi’s.

1. What the heck is the Wilson gage telling me??? The mock rounds drop in to my barrels just fine, according to the “Plunk Test”.

2. The case always stops at the ridge in the chamber, so aren’t we just making sure the bullet isn’t too long? Meaning, the “Plunk Test” only checks for bullet length?

3. Any other comments related to AOL that I’m missing?

Thanks

 

[GJSchulze]

The Wilson gauge is built to SAMMI standards. The chamber of your barrel is likely to be a little larger. The WG will only tell you if you exceed SAMMI standard length which could be longer than what will actually chamber in you gun, so the gauge is best used to be sure the cartridge isn't too fat to fit your chamber. It doesn't take much to not fit. A single granule of powder will do it so you sometimes have to blow it clean. An invisible burr can do it.

The plunk test is mostly used to determine the maximum OAL of your round that will fit the chamber without the bullet touching the rifling. This length can still be longer than what will fit your magazine or even feed correctly.

Take one that doesn't fit. Clean the WG and try it again. If that fails take some 400 grit sandpaper, wrap it around the case and spin the round to polish the case edges especially around the head. If you don't have sandpaper, put the case in head first into the gauge and twist the round a couple of times. Be careful to not jam it in hard; you are just trying to remove a tiny burr.

Now, if all or many of your rounds are having a problem I'm not sure what to tell you. At that point I'd compare a factory round to one of yours using a caliper. Do you see any bulges in the case after you seat the bullet? A round that isn't crimped enough might not fit the gauge. A straight walled case requires minimal crimping. I load 9mm and the case actually is tapered, so the case mouth can hang up just before it hits the ridge in the gauge if I miss a crimp.

Is it happening with all headstamps or just certain ones? I have had problems with certain headstamps, which I know because I sort my cases. I sorted when I started to reload to reduce one variable when troubleshooting a problem.

 

[jmorris]

It is not uncommon for cases with imperfect rims to fail a casegauge. They pass the barrel because the rim is not checked by "plunking". If the rim fails to go into the breech face then you have a malfunction despite plunk testing your rounds. This is why most competition shooters that shoot timed sports use case gauges.



There are also sizing the base of the case as well, that obviously doesn't get sized by standard size/deprime dies as the portion in question is in the shell holder.

Push through dies work for some rounds but roll sizers can even get inside extractor grooves and work for tapered cases too.

 

[jmorris]

On your 40 round that fails the gauge, drop it in the gauge backwards and give it a twist. That many times will knock the burr or dent off enough.

 

[Walkalong]

I have a tight chambered (SAMMI minimum) 9MM, so I use a Wilson gauge to check all my sized brass, and toss those that fail the gauge. I have no issues with the once loaded, as long as they pass the gauge after sizing. I do not gauge .32, .40, or .45. No issues. If I was shooting games where a failure killed your score with those calibers, I would use a gauge, or squeeze them all into submission with an FCD.

 

[Pugsbrew]

OK, retook a look at things, and still the WG is giving me fits. I can insert the cartridge backwards, and it goes in to the proper depth (the case that is). When I insert the cartridge the correct way, the entire rim, and a little of the extraction groove, protrudes. I tried dropping a bullet throughout the gage, but it gets hung up on the base. I measured the the bullet again, numerous times. and it is .400.

Now, factory ammo fits in the gage just fine.

As said before, the mock cartridge passes the plunk test. I just tried loading and extracting it in the actual weapon, seems to run fine.

The only way to get the cartridge to fit in to the WG is to seat the bullet BELOW the minimum recommended.

I think since the cartridge works in the gun, I'll just not bother with the WG any more.

Any other considerations?

Thanks again.

 

[jmorris]

Is the bullet seated crooked? Do you have any photos?

 

[fguffey]

OK, the round will “plunk” fine in the barrels, but will not drop in to the Wilson Gage. In the Wilson Gage (WG), the entire rim is proud of the gage. Now, factory ammo drop all the way in to the WG, the end of the cartridge is flush with the end of the gage. I did apply a Lee FCD crimp to the mock cartridge just to see if that made a difference, it did not.

OK, enough of this. The mock cartridge drops fine in my barrels, compared to all commercial cartridges, and the “Plunk Test” pictures. So, now for the questions.

Again, I am new at reloading semi’s.

1. What the heck is the Wilson gage telling me??? The mock rounds drop in to my barrels just fine, according to the “Plunk Test”.

I use lead blocks, wood blocks work. Your test case would work if there is no primer and no powder, I would place the Wilson case gage on the lead block then drive the case onto the Wilson case gage, then I would remove the test case and check for damage to the case and or bullet, I would also keep up with the distance the test case was driven into the gage. I would not attempt driving the case and bullet through the gage on the first swing.

In an attempt to get a reverse of the inside of the Wilson case gage I drove cases into the gage with a drift that matched the diameter of the case head while the gage was supported by a block of lead. started out easy then resistance, if anyone is thinking of attempting this procedure, do not forget to lube the case.

F. Guffey

 

[Pugsbrew]

fguffey,

It is not a case issue. The case will drop in properly every time, without the bullet. Once the bullet is seated, it will not drop properly. The mock cartridge still works great in the real barrel. The bullet is .400.

 

[rcmodel]

If the sized case fits?
But the loaded one doesn't?

And a factory round fits?
But, a reload doesn't?

And it's not seated so long the bullet is hitting the rifling and preventing it from seating all the way in the chamber?


Here's what you need to do then.

Adjust your seating & taper-crimp die so the case mouth of the loaded round measures .421" right at the case mouth.

Or in other words, exactly the same as a factory loaded round.

rc

 

[ky8]

Try what rcmodel posted.
Different numbers but this step solved all my
issues with my 9mm rounds

 

[fguffey]

It is not a case issue. The case will drop in properly every time, without the bullet. Once the bullet is seated, it will not drop properly. The mock cartridge still works great in the real barrel. The bullet is .400.

1. What the heck is the Wilson gage telling me??? The mock rounds drop in to my barrels just fine, according to the “Plunk Test”.

You seemed to think there was something wrong with the Wilson case gage. It dies not take me long to determine where something is touching especially when it is touching where it should not be ....touching, binding, holding off or has an interference fit. I have 8 9mm barrels, I do not shoot 9mm from a Wilson case gage, I shoot 9mm from a 9mm pistol.

F. Guffey

 

[Walkalong]

Since the sized case fits the gauge, and the same case after seating a bullet will not, look at trying a different seater, or seating a little at a time and rotating the case as you do, because it sounds like the bullet is not seating straight.

But yes, we do not shoot rounds from our gauge, so if if fits your barrel you'll be fine, until you run into a tight chambered gun.

I would try to solve the seating problem, even though they fit the barrel.

 

[Jim Watson]

There are a couple of things going on here.
First, the Wilson is a CARTRIDGE gauge, not a chamber checker. Since a minimum chamber must accept a maximum cartridge, the cartridge gauge is going to be smaller inside than nearly all barrel chambers. That is one reason that many rounds that will not gauge will "plunk."

Second, your gauge apparently lacks a throat or leade like a real chamber, since it will not pass your .400" bullet. Your loaded rounds are failing the gauge by the amount of bearing surface showing ahead of the case mouth. It is coming up against the front of the gauge "chamber" as the bullet hits bore diameter. Factory loads seldom have much full diameter bearing surface showing.

I don't have a .40, but my 9mm and .45 gauges have their own characteristics. After all, these are $20-$30 consumer quality gauges, not traceable to the National Bureau of Standards and likely not as close to SAAMI as you would wish.

My Wilson .45 will pass a bullet and will accept a round with a bit of SWC shoulder showing as is usual for that load.

My Lyman 9mm will pass a jacketed bullet but not cast. There is apparently a little taper to the gauge "throat" because the nose of the cast bullet will protrude out the end of the gauge before it binds. It will just barely accept my truncated cone lead bullet loads with some bearing surface showing.

My EGW "4 holer" is tighter than Wilson or Lyman even though they advertise it as having been made with chamber reamers. It has no throat whatsoever and will not accept my lead 9mms. A .45 SWC will "click" into the gauge as the shoulder bumps past the headspace surface. Jacketed bullets go in fine, if there is no other flaw in the round.

So you can gauge your sized brass, at least enough of them for some QC and to check anything that looks odd; then rely on the plunk test in a gun barrel for the loaded ammo.
Or you could visit a gunsmith with a .40 chamber reamer and have your gauge cut to chamber dimensions instead of cartridge dimensions. I did that once with a semi-wildcat; standard brass, but very long OAL with heavy bullet seated way out. The gauge was cut with the same long throat reamer as the barrel.

 

[Pugsbrew]

Jim,

Very good explanation. Thank you. I knew it couldn't be this hard trying to load for a semi.